Rubber compositions and method for treating rubber with hydroxymethyl sulfinic salts

Abstract

Rubber compositions are shown comprising diene rubber and salts of hydroxymethylsulfinic acid which exhibit improved green strength and/or tack properties. Treatment of diene rubber above 130 DEG C. with the same salts is shown to be effective in obtaining rubber compositions of improved properties.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A composition comprising diene rubber containing a modifying amount of a salt of hydroxymethylsulfinic acid and also containing carbon black or a non-black filler selected from clay, talc, silica and calcium carbonate. 
     
     
       2. The composition of claim 1 wherein the salt is of a metal ion and is present in an amount of from 0.1 to 15 parts by weight per 100 parts of diene rubber by weight. 
     
     
       3. The composition of claim 2 wherein the salt is selected from alkali metal, calcium, magnesium and zinc salts of hydroxymethylsulfinc acid. 
     
     
       4. The composition of claim 3 wherein the salt is sodium formaldehyde sulfoxylate. 
     
     
       5. The composition of claim 4 wherein the diene rubber comprises polyisoprene. 
     
     
       6. The composition of claim 3 wherein the salt is present in an amount of from 0.25 to 8 parts by weight per 100 parts of diene rubber by weight. 
     
     
       7. The composition of claim 6 wherein the salt is sodium formaldehyde sulfoxylate. 
     
     
       8. The composition of claim 7 wherein the diene rubber comprises polyisoprene. 
     
     
       9. The composition of claim 2 wherein the salt is present in an amount of from 0.5 to 5 parts by weight per 100 parts of diene rubber by weight. 
     
     
       10. The composition of claim 9 wherein the salt is selected from alkali metal, calcium, magnesium and zinc salts of hydroxymethylsulfinic acid. 
     
     
       11. The composition of claim 10 wherein the salt is sodium formaldehyde sulfoxylate. 
     
     
       12. The composition of claim 11 wherein the diene rubber comprises polyisoprene. 
     
     
       13. The composition of claim 12 wherein the diene rubber comprises natural rubber. 
     
     
       14. The composition of claim 11 wherein the diene rubber comprises a polymer from 1,3-butadiene. 
     
     
       15. The method of treating diene rubber which comprises treating the diene rubber at an appropriate temperature above 130° C. for a long enough time to impart to the diene rubber improved properties as to green strength or tack with a salt of hydroxymethylsulfinic acid wherein carbon black or a non-black filler selected from clay, talc, silica and calcium carbonate is present with the diene rubber during the treating. 
     
     
       16. The method of claim 15 wherein the treatment is performed for from 0.1 to 20 minutes at a temperature of at least 150° C. and the salt is of a metal ion and is present in an amount of from 0.1 to 15 parts by weight per 100 parts of diene rubber by weight. 
     
     
       17. The method of claim 16 wherein the salt is selected from alkali metal, calcium, magnesium and zinc salts of hydroxymethylsulfinic acid. 
     
     
       18. The method of claim 17 wherein the salt is sodium formaldehyde sulfoxylate. 
     
     
       19. The method of claim 16 wherein the diene rubber comprises polyisoprene. 
     
     
       20. The method of claim 17 wherein the treatment is performed for from 0.5 to 15 minutes at a temperature of at least 160° C. and the salt is present in an amount of from 0.25 to 8 parts by weight per 100 parts of diene rubber by weight. 
     
     
       21. The method of claim 20 wherein the salt is sodium formaldehyde sulfoxylate. 
     
     
       22. The method of claim 21 wherein the diene rubber comprises polyisoprene. 
     
     
       23. The method of claim 15 wherein the treatment is performed for from 1 to 10 minutes at a temperature of from 160° to 210° C. and the salt is present in an amount of from 0.5 to 5 parts by weight per 100 parts of diene rubber by weight. 
     
     
       24. The method of claim 23 wherein the salt is selected from alkali metal, calcium, magnesium and zinc salts of hydroxymethylsulfinic acid. 
     
     
       25. The method of claim 24 wherein the salt is sodium formaldehyde sulfoxylate. 
     
     
       26. The method of claim 23 wherein the diene rubber comprises polyisoprene. 
     
     
       27. The method of claim 25 wherein the diene rubber comprises natural rubber. 
     
     
       28. The method of claim 25 wherein the diene rubber comprises a polymer from 1,3-butadiene. 
     
     
       29. The method of claim 25 wherein the polymer is polyisoprene and the treatment comprises mastication. 
     
     
       30. The method of claim 25 wherein the polymer is polyisoprene, and the additional step of adding from 10 to 1000 parts by weight of untreated diene rubber per 100 parts diene rubber by weight. 
     
     
       31. A composition comprising polyisoprene containing a modifying amount of a salt of hydroxymethylsulfinic acid. 
     
     
       32. The composition of claim 31 wherein the salt is sodium formaldehyde sulfoxylate. 
     
     
       33. The composition of claim 31 wherein the salt is present in an amount of from 0.1 to 15 parts per weight per 100 parts polyisoprene by weight. 
     
     
       34. The method of treating polyisoprene which comprises treating the polyisoprene at an appropriate temperature above 130° C. for a long enough time to impart to the polyisoprene improved properties as to green strength or tack with a salt of hydroxymethylsulfinic acid. 
     
     
       35. The method of claim 34 wherein the salt is sodium formaldehyde sulfoxylate. 
     
     
       36. The method of claim 34 wherein the treatment is performed for from 0.1 to 20 minutes at a temperature of at least 150° C. and the salt is present in an amount of from 0.1 to 15 parts by weight per 100 parts of polyisoprene by weight. 
     
     
       37. The method of claim 34 and the additional step of adding from 10 to 1000 parts by weight of untreated polyisoprene per 100 parts polyisoprene by weight.